Testing for size-dependent trade-offs of clustering in Nephila clavipes
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Testing for size-dependent trade-offs of clustering in Nephila clavipes
Laura Sauvage (CMC ‘14)& Haley Godtfredsen (Scripps ‘16)
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IntroductionWeb ecology
• Prey capture • Males • Kleptoparasites • Predation
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Nephila clavipes
Large Medium Small
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Another component of web environment:
Solitary (built alone) Clustered (attached to other webs)
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Theoretical costs and benefits of cluster formation:
Cost = competition for food
Benefit = less predation risk per spider
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Daniella Barraza, 2012
• Cost: Medium spiders caught more prey if solitary than clustered. - No difference for small spiders.
• Benefit: Longer web tenure if clustered. - More so for medium than small spiders.
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Sauvage & Godtfredsen, 2013
Hypothesis: Costs & benefits of clustering will be size-dependent.
Preliminary data-• Frequency of
clustering• Variation in web
experience based on spider size and clustering
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Methods
• Firestone Center for Restoration Ecology• Baru, Costa Rica
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Spider ID Solitary/ Clustered
Date Found
Color Neighbor Females
Spider Size (mm)
Web Size (m)
1 S 7/5/2013 N/A N/A 1.78 0.18
2 S 7/5/2013 N/A N/A 4.74 0.43
3 C 7/5/2013 Blue 4 2.57 0.30
4 C 7/6/2013 Green 3 2.91 0.31
5 S 7/6/2013 N/A N/A 3.40 0.36
Initial Measurements
(example data)
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Spider ID
Date Web Condition
# Prey # Legs # Neighbor Females
1 7/15/2013 Good 0 8 N/A
2 7/15/2013 Good 2 8 N/A
3 7/15/2013 Poor 0 7 1
4 7/15/2013 Good 0 8 1
5 7/15/2013 Okay 1 7 N/A
Monitoring Data
(example data)
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Measuring costs and benefits of cluster formation:
Competition for food: prey capture rate
Lower predation risk● Web duration● Leg autotomy● Web condition● Reason for disappearance
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Clustering Clustered: 191 webs (48%)
Solitary: 209 webs (52%)
Frequencies of….
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Clustering Leg AutotomyClustered: 191 webs (48%) No: 367 webs (94%)
Solitary: 209 webs (52%) Yes: 25 webs (6%)
Frequencies of….
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Clustering Leg Autotomy Web FateClustered: 191 webs (48%) No: 367 webs (94%) Moved: 160 webs (65%)
Solitary: 209 webs (52%) Yes: 25 webs (6%) Depredated: 86 webs (35%)
Frequencies of….
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Clustering Prey Capture
Leg Autotomy
Spider/Web Fate
Spider Size NS + NS NS
Influence of spider size on …
NS = not significant+ = positive correlation
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Clustering Prey Capture
Leg Autotomy
Spider/Web Fate
Spider Size NS + NS NS
Influence of spider size on …
Influence of clustering on …Prey
CaptureLeg
AutotomySpider/Web
Fate
Clustered compared to Solitary
NS NS NS
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Significance ● Studying the
costs/benefits of living in a group (cluster)
● Do these trade-offs differ with spider size?
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Prey capture
Preliminary Data
Predation
Spider Size
Clustering X X
X
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To Be Determined
• Do size-dependent trade-offs
exist in clusters?● Frequency with which spiders
of different sizes are clustered or
solitary.
• Cluster formation
• Order of arrival
• Effect of size
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Acknowledgements
Keck Science Department Professor E. Ferree
Professor D. McFarlaneGreddy Arias-- Firestone Caretaker
Pitzer College
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Preliminary ResultsM
ean
web
dia
met
er (m
m)
Bigger spiders have bigger webs.
n=17
n=183n=138